1. The Technical Field
The present invention relates to fuel injectors for internal combustion engines.
2. The Prior Art
In its simplest conception, a fuel injector for an internal combustion engine is a high frequency, short stroke valve that permits fuel to be incrementally introduced, under substantial pressure, into an engine cylinder. Typically, an injector includes the following functional components: a body; an jet needle and tappet rod, configured for reciprocating movement within the body; some sort of biasing device (e.g., a coil spring) for biasing the jet needle and tappet rod toward the closed (or open) position with respect to the fuel inlet aperture into the cylinder; and some sort of motive mechanism (e.g., a magnetic solenoid-like arrangement) for transiently and intermittently moving the jet needle from the closed (or open) position to an open (or closed) position. The far end of the jet needle, in the closed position, rests in a seat formed on the outside of the cylinder head. The fuel flows through the body of the injector, typically from an inlet in the body (usually remote from the seat), around the jet needle and tappet rod, and out through the aperture into the cylinder (when the jet needle is moved away from the seat).
In typical prior art injectors, the fuel comes into direct contact with the tappet rod, the biasing device, and even possibly components of the motive mechanism. Due to the corrosive nature of most fuels, this may have the result of causing premature degradation of one or more of the internal moving components of the injector.
Accordingly, it would be desirable to provide a structure for isolating sensitive moving parts within a fuel injector, from exposure to potentially corrosive fuel, without adversely affecting the performance of the injector and/or significantly increasing the cost of the injector.
These and other desirable characteristics of the invention will become apparent in light of the present specification and drawings.
The invention comprises, in part, a seal for a fuel injector for an internal combustion engine, wherein the fuel injector includes an injector body surrounding a reciprocating injector jet needle, supported by a tappet rod, an end of the tappet rod extending into an enclosure within the injector body, surrounding one or more structures for enabling the supported reciprocating movement of the injector jet needle, for providing a liquid-tight seal between the tappet rod and the enclosure, for precluding the intrusion of liquid fuel into the enclosure.
The seal for a fuel injector for an internal combustion engine comprises a flexible bellows member, including a first cap sealingly joined to a second cap. The first cap includes a first collar for connection to one of a tappet rod of a fuel injector and regions proximate an aperture into an enclosure through which a tappet rod of a fuel injector passes, the first cap further including a substantially radially extending flare and a second collar. The second cap includes a first collar for connection to the other one of regions proximate an aperture into an enclosure through which a tappet rod of a fuel injector passes and a tappet rod of a fuel injector, the second cap further including a substantially radially extending flare and a second collar. The second collar of the first cap is sealingly joined to the second collar of the second cap, whereupon installation of the seal into a fuel injector, the seal precludes intrusion of liquid fuel at the aperture of the enclosure.
The seal preferably has a longitudinal axis. The second collar of the first cap is a substantially cylindrical member concentric to the longitudinal axis; the second collar of the second cap is a substantially cylindrical member concentric to the longitudinal axis; and the second collar of the first cap is insertingly received within the second collar of the second cap.
The second collar of the first cap is sealing affixed to the second collar of the second cap preferably by a braze or weld.
The first and second caps are preferably formed by stamping.
The first and second caps are preferably fabricated from a liquid fuel resistant material. The first and second caps are preferably fabricated from stainless steel.
The invention also comprises, in part, a fuel injector for an internal combustion engine, comprising an injector body; a reciprocating injector jet needle in the injector body, supported by a tappet rod, an end of the tappet rod extending into an enclosure within the injector body, the enclosure surrounding one or more structures for enabling the supported reciprocating movement of the injector jet needle; and a fuel injector seal for providing a liquid-tight seal between the tappet rod and the enclosure, for precluding the intrusion of liquid fuel into the enclosure.
The seal further comprises a flexible bellows member, including an first cap sealingly joined to an second cap. The first cap includes a first collar connected to one of the tappet rod of the fuel injector and the aperture into the enclosure through which the tappet rod of the fuel injector passes, the first cap further including a substantially radially extending flare and a second collar. The second cap includes a first collar connected to the other of the aperture into the enclosure through which the tappet rod of the fuel injector passes and the tappet rod of the fuel injector, the second cap further including a substantially radially extending flare and a second collar. The second collar of the first cap is sealingly joined to the second collar of the second cap. The seal precludes intrusion of liquid fuel at the aperture of the enclosure.
Preferably, the seal has a longitudinal axis; the second collar of the first cap is a substantially cylindrical member concentric to the longitudinal axis; the second collar of the second cap is a substantially cylindrical member concentric to the longitudinal axis; and the second collar of the first cap is insertingly received within the second collar of the second cap.
The second collar of the first cap is sealing affixed to the second collar of the second cap by a braze or weld.
Preferably, the first and second caps are formed by stamping.
Preferably, the first and second caps are fabricated from a liquid fuel resistant material, preferably stainless steel.
The present invention also comprises, in part, a method for manufacturing a seal for a fuel injector for an internal combustion engine, wherein the fuel injector includes an injector body surrounding a reciprocating injector jet needle, supported by a tappet rod, an end of the tappet rod extending into an enclosure within the injector body, surrounding one or more structures for enabling the supported reciprocating movement of the injector jet needle, for providing a liquid-tight seal between the tappet rod and the enclosure, for precluding the intrusion of liquid fuel into the enclosure, the method for manufacturing a seal for a fuel injector for an internal combustion engine comprising:
forming a flexible bellows member, including a first cap sealingly joined to a second cap;
forming the first cap to include a first collar for connection to one of a tappet rod of a fuel injector and regions proximate an aperture into an enclosure through which a tappet rod of a fuel injector passes, the first cap further including a substantially radially extending flare and a second collar;
forming the second cap to include a first collar for connection to the other of regions proximate an aperture into an enclosure through which a tappet rod of a fuel injector passes and a tappet rod of a fuel injector, the second cap further including a substantially radially extending flare and a second collar;
sealingly joining the second collar of the first cap to the second collar of the second cap;
whereupon installation of the seal into a fuel injector, the seal precludes intrusion of liquid fuel at the aperture of the enclosure.
The method further comprises the steps of
forming the seal with a longitudinal axis;
forming the second collar of the first cap as a substantially cylindrical member concentric to the longitudinal axis;
forming the second collar of the second cap as a substantially cylindrical member concentric to the longitudinal axis;
inserting the second collar of the first cap within the second collar of the second cap.
The method preferably further comprises the step of:
sealingly affixing the second collar of the first cap to the second collar of the second cap by a braze or weld.
The method preferably further comprises the step of forming the first and second caps by stamping.
The method may further comprise the step of fabricating the first and second caps from a liquid fuel resistant material, preferably stainless steel.